Ceramic core electromagnetic forming coil

ABSTRACT

A forming element is described for use in magnetic forming apparatus. The forming element includes a conductor and a support member comprised of ceramic material. The support member, in addition to supporting the conductor, affords a vehicle for conducting heat from the conductor.

United States Patent 'Filed Inventors Appl. No.

Patented Assignee CERAMIC CORE ELECTROMAGNETIC FORMING COIL PrimaryExaminer- Richard .1. Herbst AltorneyAnderson, Luedeka, Fitch, Even andTabin 8 Claims, 7 Drawing Figs.

US. Cl 72/56, ABSTRACT: A forming element is described for use in mag29/421 netic forming apparatus. The forming eflement includes a con-Int. Cl B2ld 26/14 ductor and a support member comprised of ceramicmaterial. Field of Search 72/56; The support member, in addition tosupporting the conductor,

29/421 M; 336/208 affords a vehicle for conducting heat from theconductor.

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ar la PAIENTED mm 7 law FIGJ SHEET 1 [IF-'3 CERAMIC CORE ELECTROMAGNETICFORMING COIL This invention relates to forming apparatus and, moreparticularly, to apparatus for forming material by energy acquired froma varying magnetic field.

Apparatus has been developed for forming materials by employing varyingmagnetic fields of high intensity. An example of such apparatus is shownand described in the U.S. Pat. No. 2,976,907, issued Mar. 28, 1961, andassigned to the assignee of the present invention. In apparatus of thisgeneral type, an electric current pulse of high amperage is passedthrough a forming element comprising a conductor (e.g., in the form of acoil) to provide a desired magnetic field of high intensity. The currentpulse may be applied to the conductor directly from a current pulsesource or may be induced in the conductor by suitable inductive elementspositioned adjacent thereto.

A conductive workpiece, positioned in thepulsed magnetic field producedby the conductor, has a current pulse induced in it. This current pulseinteracts with the pulsed magnetic field to produce a force acting onthe workpiece. If the force is sufficiently strong, a deformation of theworkpiece results. The shape of the deformation is dependent upon thedistribution in time and space of the magnetic field and the position ofthe workpiece relative to the field. Repeated pulses of current may beapplied to or induced in the conductor, thus causing a series ofdeforming impulses to act upon the workpiece.

The conductors used in magnetic forming apparatus are subject to severeforces during forming of the workpiece. In order that a nonyieldingreaction will be furnished to the mechanical forces associated with thehigh strength magnetic field, the conductor is supported againstmovement relative to the workpiece. In the case of a helical coil, suchsupport may be furnished in the form of a cylindrical support memberpositioned within the helical conductor with its outer surface incontact therewith and coaxial therewith. In the case of a spiralconductor configuration, the support therefor may be furnished by asuitable planar support member positioned in contact with one side ofthe conductor perpendicularly of the axis thereof. In order to avoidcurrent flow, and hence a reduction in the efficiency of the formingapparatus, the support member utilized should have a high dielectricstrength (i.e., high electrical resistance). Typical materialsheretofore utilized as support members, such as composites offiberglass, although having high compression strength, have alsoexhibited a low modulus of elasticity, typically considerably lower thanthe material of the conductor itself. As a result, loading forcestransmitted by the conductor to the support member may cause excessivecompression thereof and a corresponding excessive strain on theconductor. Energy stored in the support member as a result of thecompression can result in oscillation, conductor damage from rebound,and deterioration due to fatigue.

During operation of magnetic forming apparatus, repeated pulsingproduces a considerable amount of heat in the conductor due to ohmiclosses therein. If such heat is not adequately removed, structuraldamage to the conductor may result. In addition, a high operatingtemperature may cause a reduction in efficiency due to an increase inthe resistance of the conductor to the passage of current therethrough.Accordingly many conductors in magnetic forming apparatus have been madehollow and a cooling fluid has been circulated through the conductoritself. As a result, the number of possible coil designs has beensomewhat limited due to the necessity for incorporating coolant flowpassages in the conductor.

It is an object of this invention to provide improved magnetic formingapparatus.

Another object of the invention is to provide magnetic forming apparatusin which forces loading the conductor are transferred to a supportingmember with a minimum strain on the conductor.

A further object of the invention is to provide magnetic formingapparatus in which cooling of the conductor is effected withoututilizing coolant flow passages in the conductor.

Other objects of the invention will become apparent to those skilled inthe art from the following description, taken in connection with theaccompanying drawings wherein:

FIG. 11 is a full section side view of magnetic forming apparatusconstructed in accordance with the invention;

FIG. 2 is an end elevational view of the apparatus of FIG. 1;

FIG. 3 is a partial side elevational view of the apparatus of FIGS. 1and 2;

FIG. 4 is a full section side view of a portion of a further embodimentof the invention;

FIG. 5 is an end section view of still a further embodiment of theinvention;

FIG. 6 is a side elevational view of the apparatus of FIG. 5; and

FIG. 7 is a full section side view of a still further embodiment of theinvention.

Very generally, the apparatus of the invention, as illustrated herein,comprises a conductor responsive to pulses of electrical energy appliedthereto to conduct a current for producing a magnetic field for forminga workpiece disposed in the mag netic field. A support member supportsthe conductor and is comprised of ceramic material. The support memberhas a uniform unbroken surface. The conductor is of square orrectangular cross section and has one surface which mates with theuniform surface of the conductor to conduct a substantial amount of heatfrom the conductor. Means are provided for removing heat from thesupport member to thereby cool the conductor.

Referring now particularly to FIGS. 1 to 3, the apparatus illustratedtherein is for producing an expansion type deformation in a workpiecewhich is positioned surrounding the conductor 11. The working part ofthe conductor 11 consists of a series of helical turns 12, the conductorin this region being of a relatively flat rectangular cross section. Theconductor further includes a pair of hollow cylindrical sections 13 and14, one at each end of the section of helical turns l2. A rela' tivelywide opening or gap 16 is provided between the cylindrical section 14and the adjacent helical winding 12 to provide a flux return path forthe magnetic field established by the conductor. A similar opening orgap 17 is provided between the cylindrical section 113 and the closestof the helical loops 12.

Current is supplied to the conductor 111 through a broad flat terminalplate 18. The terminal plate is provided with a slit 19 therein and witha central opening 21 through which the cylindrical section 13 of theconductor lll passes. The cylindrical section 13 is secured to the plate18 by means of a bolt, not illustrated, which passes through anappropriate hole 22 in the terminal plate near the end of the slot 119to draw the opposite faces of the slot toward each other and thus clampthe cylindrical section 13 in the opening 21. Suitable means, notillustrated, are connected to the terminal plate 113 for supplyingcurrent pulses thereto.

The current pulse, after passing through the conductor lll, is returnedvia a return conductor 23. The return conductor 23 consists of a tubelocated coaxial with the axis of the helical turns 112 of the conductorIll. The return conductor 23 is connected to the cylindrical section Mof the conductor 1111 by means of an end fitting 24 of conductivematerial. The fitting 2% has a projection 26 through which an opening 27is provided, and has a circular outer periphery which mates with theinner wall of the cylindrical section M. The return conductor 23 fitswithin the opening 27 in contact with the end fitting 24.

The outer surface of the conductor II is covered by an outer sheet 28 ofa suitable insulating material, such as epoxy. An end cover 29 of asuitable insulating material closes the open end of the cylindricalsheet 28 and covers the end fitting 24 and the end of the returnconductor 23. The edge of the cylindrical outer sheet seats in anannular recess 31 provided in the outer periphery of the end cover 29.

The end of the return conductor 23 opposite the end fitting 24 issurrounded by a cylindrical return conductor terminal 32, passingthrough a central opening 33 therein and in contact therewith. Thereturn conductor terminal 32 is supported within a circular opening 34in a projecting portion 36 of a return conductor terminal plate 37. Theprojecting portion 36 of the plate 37 defines a generally U-shapedrecess 38 within which the inner end of the return conductor terminal 32terminates. A split or slot 39 is provided in the return conductorterminal plate 37. The return conductor terminal 32 is clamped in theopening 34 by means of a bolt, not shown, extending through a hole 41provided near the open end of the slot 39. When the bolt is tightened,the opposite faces of the slot 39 are drawn toward each other, thusclamping the return conductor terminal 32 in the opening 34. Theterminal plate 37 and the terminal plate 18 are secured together againsta layer 42 of insulating material by suitable insulated means, notillustrated, such as bolts.

The conductor 11 is supported internally by a support member 43. Theouter surface of the support member is cylindrical and is uniform andunbroken, that is, uninterrupted by grooves or other irregularities. Therectangular cross section conductor has its inner surface in matingcontact with the cylindrical surface of the support member. The supportmember 43 is hollow, having a generally cylindrical inner surface 44 foraccommodating the return conductor 23. During operation of theapparatus, the conductor 11 is subject to high forces acting radiallyinward. In order to resist such forces with minimum strain of theconductor, the support member 43 is comprised of a dense ceramicmaterial which exhibits good electrical insulating properties and a veryhigh compression strength and high modulus of elasticity and anexceptionally high thermal conductivity. Two dense ceramic materialswhich are of particular advantage are aluminum oxide (A1 and berylliumoxide (Be0). (Be0 has a thermal conductivity close to that of aluminummetal). As a result, deformation of the metallic conductor 11 duringoperation of the apparatus is minimized, the conductor loading beingtransferred to the I ceramic support member with minimum strain of theconductor. The large flat" surface area of engagement between theconductor and the support member provides good thermal transfer anddistributes bearing loads evenly.

During magnetic forming operations which require repeated and rapidpulsing of current through the conductor, the conductor may heat up dueto ohmic losses therein. The configuration of the apparatus illustratedin FIGS. 1 to 3, and the particular material of which the support member43 is constructed, enables efficient cooling of the conductor to beaccomplished without the necessity of providing coolant passages withinthe conductor itself. An annular gasket or seal 46 is provided betweenthe end of the support member 43 and the end fitting 24. This seals theregion within the hollow conductor 43 from the outside at the projectingend. The return conductor 23 is made hollow, defining a passage 47. Theouter wall of the return conductor 23 and the inner wall 44 of thesupport member 43 are spaced from each other to define a passage 48. Oneor more openings 49 are provided in the return conductor 23. Theopenings 49 communicate between the passage 47 and the passage 48. Aconnector'tube 51 is provided communicating with the passage 47 at theend thereof opposite the openings 49. The tube 51 is adapted forconnection to a source of pressurized coolant, such as a source ofpressurized water, such that coolant flows axially through the passage47 and is then forced through the openings 49 into the passage 48.

The return conductor terminal 32 is spaced axially from the closest endof the support member 43, defining an annular chamber 53. The passage 48terminates in the annular chamber 53 and coolant accumulating in theannular chamber 53 is passed througha passage 54 provided in the returnconductor terminal 32 into a connector tube 56 attached thereto.Suitable means, not illustrated, are connected to the tube 56 forcollecting the outflowing coolant from the tube. Because of the ceramicmaterials strength, its impervious character, and its exceptionally highthermal conductivity for an electrical insulator, the support member 43readily transfers heat from the conductor 11 to the coolant flowingthrough the passage 48. Because of this, the conductor 11 may be madesolid, rather than having coolant passages therein, allowing for greaterflexibility in design.

In order to seal the annular chamber 53 against leakage of coolant intothe recess 38, a seal sleeve 57 is provided. The sleeve 57 extends overthe outer periphery of the chamber 53 and beyond the edges thereof asufiicient distance as to allow the use of a pair of annular seals 58and'59 near the opposite ends of the sleeve 57. This seals the chamber53 against leakage. The resultant construction makes possible thepositioning of the two tubes 51 and 56 adjacent each other, affordingsome convenience in design. Moreover, the compliant nature of thearrangement of the sleeve 57 and the seals 58 and 59 avoids theaccidental application of undesirable forces to the ceramic supportmember 43 during assembly or operation. Under some circumstances, arigid seat termination of the support member 43 within the returnconductor terminal plate 37 may cause excessive loading and damage tothe support member through minor misalignment of its parts duringassembly or through vibration of the parts during operation.

in the event that extraneous loads on the supported end of the supportmember can be tolerated, and that nonadjacent positioning of the inletand outlet coolant connections can also be tolerated, the apparatus ofthe invention may be constructed as illustrated in FIG. 4. In theembodiment of FIG. 4, parts therein having functions identical withparts in the embodiment of FIGS. 1 to 3 have been given identicalreference numbers preceded by a one. Thus, the conductor 111, having aplurality of helical turns 112, is supported on a dense ceramic hollowsupport member 143. A support cylinder 161 of a suitable rigidinsulating material is disposed coaxially around the cylindrical section113 of the conductor 111. The outer sheet 128 of insulation extends withthe cylindrical section 113 through an opening in the cylinder 161, theentire assembly thereby being supported or cantilevered out by thecylinder. The cylinder 161 is provided with an annular flange 162 andextends through an opening 163 in a plate 164 of insulating material,the flange 162 seatingin an annular recess about the periphery of theopening 163. I

The cylindrical section 113 of the conductor 111 projects beyond theflanged end of the supporting cylinder 161 and is clamped within theterminal plate 118. The terminal plate 118 is split or slotted at 119and is provided with a bolt hole 122 for clamping the opposite faces ofthe slot 119 toward each other and thereby clamping the cylindricalsection 113 within the opening 121 provided in the terminal plate 118.An input conductor plate 166 is bolted to the terminal plate 118 forconducting current pulses thereto.

The return conductor 123 consists of two layers-copper sheath overstainless steel. The return conductor which, as in the previouslydescribed embodiment, extends through the hollow interior of the supportmember 143, is clamped in an opening 167 in the return conductorterminal plate 137. The return conductor terminal plate 137 is brazed tothe return conductor 123 in electrical contact with the terminal plate137. The opening 167 is provided with a series of sections or steps ofdifferent diameters and thereby also accommodates the end of the supportmember 143. An annular seal 168 is provided surrounding the end of thesupport member 143 between the support member and the return conductorterminal plate 137. The next adjacent step-in the opening 167 issufficiently large to provide a space 170 between the return conductor123 and the return conductor terminal plate 137. The seal 168 seals thisspace. Current is conducted from the return conductor terminal plate 137by a conductive plate 169 bolted thereto.

A fitting 171 is bolted to the return conductor terminal plate 137 overthe end of the return conductor 123. The fitting 171 includes a recess172 and a passage 173 for inlet coolant which forms a fluid path to theinterior of the return conductor 123. The recess 172 is sealed by anannular seal 175 which surrounds the recess at the interface between thereturn conductor terminal plate 137 and the fitting 171. Coolant flowingthrough the return conductor is returned through the passage 148 outsidethe return conductor to the space 170 between the opening 167 and theouter surface of the return conductor 123. This space is drained by apassage 174 in the return conductor terminal plate 137. The passage 174is shown in dotted lines since it is out of its normal position in thedrawing by 90.

Under some circumstances, the high heat transfer capacity of the denseceramic material of the support member for the conductor may allow anarrangement such as is illustrated in FIGS. and 6. In the embodiment ofFIGS. 5 and 6, parts therein having functions similar to parts in theembodiment of FIGS. 1 to 3 have been given identical reference numberspreceded by the number 2. Thus, the embodiment of FIG. 5 and 6 includesa conductor 21] having a plurality of helical turns 212 and a pair ofcylindrical sections 213 and 214 at opposite ends. The conductor 211 isdisposed upon a hollow cylindrical support member 243 of a dense ceramicmaterial and is covered by an outer sheet 228 of insulating material.The outer sheet 228 is closed at one end by an end cover 229, also ofinsulating material.

In the embodiment of FIGS. 5 and 6, the return conductor 223 is solid,no coolant being passed therethrough. Electrical connection between thesolid conductor 223 and the cylindrical section 214 of the conductor 211is made by means of a conductive end fitting 224. The fitting 224 isgenerally circular in shape and has a central opening therein foraccommodating the solid return conductor 223. A terminal plate 210conducts current pulses to the cylindrical section 213 of the conductor211. The terminal plate 218 is provided with a thick section 276 and hasa split or slot 219 therein and a central opening 221 in which thecylindrical section 213 is accommodated. A bolt hole 222 allows thefacing surfaces in the slot 219 to be drawn toward each other and thusclamp the cylindrical section 213 in the terminal plate 218. Since thesupport member 243 has an outer surface in mating engagement with theinner surface of the cylindrical section 213, the support member is alsoclamped within the terminal plate opening 221. As may be seen in FIG. 5,the thickened section 276 of the terminal plate 218 is provided withfluid conducting passages 277 and 278 therein. The passage 277 includesan inlet orifice 279 and an outlet orifice 281. Similarly, the passage278 includes an inlet orifice 282 and an outlet orifice 283. Thepassages 277 and 278 are bored through the thickened section 276 andare, therefore, sealed with plugs 284 and 286, respectively.

The return conductor 223 passes beyond the end of the support member 243and fits within an opening 267 in a return conductor terminal plate 237.The terminal plate 237 includes a thickened portion 287 and is shown asa solid member in which the opening 267 is provided and in which thesolid conductor 223 may be force fit or welded for proper connection.Alternatively, a split plate connection in the terminal plate 218 mayalso be utilized, as shown in the previous embodiments. The terminalplate 218 and 237 are separated by a layer of insulation 242, beingbolted against opposite sides thereof by suitable means, notillustrated.

The high thermal conductivity of the ceramic material of the supportingmember 243 enables the supporting member to conduct heat from theconductor 211 to the heat sink in the terminal plate 218. Accordingly,no fluid circulation need be provided within the support member 243,making the construction somewhat simpler than in the previous describedembodiments.

In the previously described embodiments, the nature of the conductor wassuch as to provide expansion deformation forces on a workpiecepositioned around the conductor. If unidirectional forces rather thanradial forces are desired, a construction such as is shown in FIG. 7 maybe utilized. The conductor 301 therein is of generally square crosssection and includes a plurality of turns 302 in the form of a flatspiral. When current pulses are passed through the windings 302, forcesare produced which are exerted generally parallel with the axis of thespiral (vertical in the drawing). in order to support the conductor 301against such forces, a support member 303 is provided. The supportmember 303 has a generally circular outer periphery and is of athickness about l/7th to rlith the diameter. A central opening 304,elongated in the direction perpendicular to the paper in the drawing, isprovided in the support member 303. A high voltage conductor plate 306is passed through the opening 304 and is secured in electrical contactto the innermost end of the spiral conductor 301.

The support member 303 rests in an annular recess 307 formed in a returnconductor ring 300. The upper surface of the support member 303 is flushwith the upper edge of the ring 308, and the outermost turn of theconductor 301 is bolted to the return conductor ring 308 by a pluralityof bolts 309. The bolts 309 also secure a flat sheet 311 of insulatingmaterial over the top surface of the conductor 301 for protecting same.

A fluid manifold 312 is provided just beneath the support member 303.The fluid manifold 312 is of an electrically conductive material and isprovided with a central opening 313 therein for accommodating the plate306 in a spaced relation to prevent shorting. The upper surface of thefluid manifold 312 is provided with an annular recess 314 therein, andis also provided with a pair of concentrically disposed ring seals 316and 317 for sealing the recess 314 against the underside of the supportmember 303. A fluid conducting inlet tube 310 passes through the fluidmanifold 312 and communicates with the recess 314 at one side thereof.At the opposite side, a fluid drain tube 319 communicates with therecess 314, passing through the fluid manifold 312. The fluid manifoldis secured and clamped to the underside of the support member 303 by aclamping ring 321 which extends around the lower edge of the terminalring 308 and extends inwardly of the inner surface thereof to overlapthe fluid manifold 312 on its lower surface. A plurality of bolts 322are provided to secure the clamping ring 321 against the terminal ring300..

The electrical return for the conductor 302 is provided by a returnconductor plate 323. The plate 323 is provided with a flange 324extending outwardly near its upper edge. The flange 324 is capturedbetween the lower surface of the fluid manifold 312 and a lower coverplate 326. The lower cover plate 326 is secured to the clamping ring 321by a plurality of bolts 327, and is provided with openings 320 and 329therein for accommodating the tubes 313 and 319, respectively. A sheet331 of insulation material is disposed between the conductive plates 306and 323. Accordingly, flow of current pulses to the conductor 302 isthrough the plate 306 to the cen termost termination of the conductor.Return flow is from the outer periphery of the conductor through theterminal ring 300, the fluid manifold 312, the flange 324 and theconductor 323.

The material of which the support member'303 is comprised is the same asthat described in connection with the support members of the previousembodiments. Accordingly, the thermal conductivity thereof is relativelyhigh and heat is adequately removed from the conductor 301 through thesupport member 303 to the coolant circulated in the recess 314.Moreover, because of the high compression strength and high modulus ofelasticity of the material, good support is given to the conductoragainst deforming forces such that strain on the conductor is minimized.Good thermal transfer and load dis tribution is attained due to theeffect of one surface of the rectangular or square cross sectionconductor being flush or in mating engagement with the uniform unbrokensurface of the support member.

It may therefore be seen that the invention provides improved magneticforming apparatus in which satisfactory support for the conductor of theapparatus is provided with minimum strain exerted on the conductorduring high current periods. Moreover, satisfactory heat removal fromthe conductor is possible without the necessity of providing for coolantpassages within the conductor itself.

Various modifications of the invention in addition to those shown anddescribed herein will become apparent to those skilled in the art fromthe foregoing description and accompanying drawings. Such modificationsare intended to fall within the scope of the appended claims.

We claim:

1. A forming element for use in magnetic forming apparatus, comprising,a conductor having a plurality of turns and being responsive to pulsesof electrical energy applied thereto to conduct a current for producinga magnetic field for forming a workpiece in the magnetic field, asupport member comprised of ceramic material positioned in directcontact with said conductor on the side thereof opposite to the work- Ipiece for supporting said conductor against forces exerted on saidconductor during forming of a workpiece, and means for removingsufficient heat from a surface of said support member opposite theconductor to cool said conductor, said support member being a solidcontinuous mass with a uniform unbroken supporting surface extendingacross the gaps between the turns of said conductor, and said conductorbeing of rectangular cross section and having one surface flush againstsaid supporting surface of said support member along the length of saidconductor providing a substantial area of direct contact therebetween.

2. A forming element according to claim 1 wherein said conductor is ofhelical configuration and wherein the supporting surface of said supportmember is cylindrical and is coaxial with said helical conductor.

3. A forming element according to claim 1 wherein said conductor is ofspiral configuration and wherein said supporting surface of said supportmember is planar and is perpendicular to the axis of said spiralconductor.

4. A forming element according to claim 1 wherein said heat removingmeans include a heat sink in contact with a further surface of saidsupport member, and further include means for passing a circulatingfluid coolant in contact with a surface of said heat sink.

5. A forming element according to claim 1 wherein the ceramic materialof which said support member is comprised consists of beryllium oxide.

6. A forming element according to claim 2 wherein said support member ishollow, said forming element further including a return conductorcomprising a hollow tube disposed centrally of said support member forproviding a return current path from said conductor, said returnconductor being spaced radially from the inner wall of said supportmember to form a pair of concentric coolant flow passages.

7. A forming element according to claim 6 including coolant conductingmeans spaced axially from one end of said support member, and includinga seal sleeve disposed about the space between said coolant conductingmeans and said support member to define a chamber for coolant flowbetween said coolant conducting means and said support member withoutdirect contact therebetween.

8. A forming element according to claim 2 wherein said support member ishollow, said forming element including a return conductor extendingthrough the hollow interior of said support member for conductingcurrent from said conductor, and a fluid cooled heat sink disposed incontact with one end of said support member for removing heat therefrom.

1. A forming element for use in magnetic forming apparatus, comprising,a conductor having a plurality of turns and being responsive to pulsesof electrical energy applied thereto to conduct a current for producinga magnetic field for forming a workpiece in the magnetic field, asupport member comprised of ceramic material positioned in directcontact with said conductor on the side thereof opposite to theworkpiece for supporting said conductor against forces exerted on saidconductor during forming of a workpiece, and means for removingsufficient heat from a surface of said support member opposite theconductor to cool said conductor, said support member being a solidcontinuous mass with a uniform unbroken supporting surface extendingacross the gaps between the turns of said conductor, and said conductorbeing of rectangular cross section and having one surface flush againstsaid supporting surface of said support member along the length of saidconductor providing a substantial area of direct contact therebetween.2. A forming element according to claim 1 wherein said conductor is ofhelical configuration and wherein the supporting surface of said supportmember is cylindrical and is coaxial with said helicAl conductor.
 3. Aforming element according to claim 1 wherein said conductor is of spiralconfiguration and wherein said supporting surface of said support memberis planar and is perpendicular to the axis of said spiral conductor. 4.A forming element according to claim 1 wherein said heat removing meansinclude a heat sink in contact with a further surface of said supportmember, and further include means for passing a circulating fluidcoolant in contact with a surface of said heat sink.
 5. A formingelement according to claim 1 wherein the ceramic material of which saidsupport member is comprised consists of beryllium oxide.
 6. A formingelement according to claim 2 wherein said support member is hollow, saidforming element further including a return conductor comprising a hollowtube disposed centrally of said support member for providing a returncurrent path from said conductor, said return conductor being spacedradially from the inner wall of said support member to form a pair ofconcentric coolant flow passages.
 7. A forming element according toclaim 6 including coolant conducting means spaced axially from one endof said support member, and including a seal sleeve disposed about thespace between said coolant conducting means and said support member todefine a chamber for coolant flow between said coolant conducting meansand said support member without direct contact therebetween.
 8. Aforming element according to claim 2 wherein said support member ishollow, said forming element including a return conductor extendingthrough the hollow interior of said support member for conductingcurrent from said conductor, and a fluid cooled heat sink disposed incontact with one end of said support member for removing heat therefrom.